3.90 vs 4.10

[MunsterZ28]

im getting new gears in my rear end but dad says 3.90 over 4.10

id like to no the diffrence in gas and more important 1/4 mile times between the two.

thanks for the help

1996 z28 cammed m6

[1BADAIR]

I don't think they make a 3.90 for a 10 bolt do they?
as for et differances that is an open question. HP, RPM,tire size and more get factoredin for that

[MunsterZ28]

I don't think they make a 3.90 for a 10 bolt do they?
as for et differances that is an open question. HP, RPM,tire size and more get factoredin for that

to be honest i dont know if they make 3.90s for a 10 bolt. i dont know much about rear ends

[lozanoa11]

if they do there can't be a big difference between the two. if you were splitting hairs then yes but if its street/strip cant see the diffence being extreamly noticable

[JoeliusZ28]

motive makes a 3.90 for the 10 bolt.

One thing to keep in mind is that a 4.11 (not 4.10) is actually a stronger gear than the 3.90 because of the tooth counts

3.90 = 10 pinion 39 ring
4.10 = 10 pinion 41 ring
4.11 = 9 pinion 37 ring

less teeth = stronger.

[1BADAIR]

3.90's are always noiseyer also

[my95z28]

I would also like to know, going from stock 3.42 (I think) to a 4.10 what is going to be mpg diference and E.T changes?

[Orange Terror]

There's a range of ratio you want to achieve for first gear for launching. From what I can find you should have a 2.66 first gear ratio. Assuming you have a 26 inch tall tire, multiply the first gear ratio X the rear. You want this to fall between 8 -10. The farther over 10, the more like a creeper it will be, under 8, and you lose that grunt that you want.

2.66 X 3.90 = 7.9:1
2.66 X 4.10 = 10.9:1

So, if you want my recommendation, 3.73 would be perfect, gives you a 9.92:1. Yes, you will lose a little mileage probably, but with a 6 speed I can't believe it will be much, that's not a big jump. And if your tires are larger or smaller in overall height than 26 inches, you will have to adjust what your rear gear would be.

[JoeliusZ28]

MPG differences on an m6 car are slim to none. gains in the quarter are usually a couple tenths.